Moreover, we also detected the protein levels of PCNA and MMP9 in tumors and found that silenced circ_100565 obviously suppressed the protein levels of PCNA and MMP9 in tumors (Fig. 3d), indicating that circ_100565 inhibited the proliferation and metastasis of NSCLC tumor, thereby reducing the tumor growth of NSCLC. Here, PCNA is linked to neoplasm.